1. FIELD OF THE INVENTION
The present invention relates to a rear end cross member of automobile, and more particularly to a rear end cross member reinforcement structure of automobile constructed to reinforce a structural strength to a joint area between both tip end portions of rear end cross member and a quarter panel to enable to fully withstand an external force even if the external force such as distortion or the like is applied thereto.
2. DESCRIPTION OF THE PRIOR ART
Generally, an automobile is composed of a body and a chassis, where the body comprising an external appearance of the automobile includes a plurality of various shapes of members, each appropriately combined therebetween. A rear body of an automobile equipped with a tailgate (T) at a rear end thereof includes a rear end cross member 10 and a quadrant panel 12 (hereinafter referred to as quarter panel) joining both tip end portions of the rear end cross member 10, where a joined portion between the rear end cross member 10 and the quarter panel 12 is illustrated in FIG. 2 showing xe2x80x9cPxe2x80x9d portion in FIG. 1.
As illustrated in FIG. 3 showing a sectional view taken along line Axe2x80x94A, the rear end cross member 10 is constructed to form a closed section by an upper rear end cross member 10a, a lower rear end cross member 10b and an outer rear end cross member 10c, where both tip end portion of the rear end cross member 10 are joined by the quarter panel 12 as shown in FIG. 4 illustrating a sectional view taken along line Bxe2x80x94B. The quarter panel 12 is constructed to include an inner lower quarter panel 12a joining a tip end portion of the lower rear end cross member 10b and an outer quarter panel 12b joining a tip end portion of the outer rear end cross member 10c. 
Furthermore, as illustrated in FIG. 5 for showing a sectional view taken along line Cxe2x80x94C of FIG. 3, the quarter panel 12 further includes an inner lower quarter extension panel 12c joining a tip end portion of the upper rear end cross member 10a and an inner quarter panel 12d joining a tip end portion of the inner lower quarter extension panel 12c, where a tip end of the lower rear end cross member 10b at the rear end cross member 10 is joined by the inner lower quarter panel 12a and a tip end portion of the inner lower quarter panel 12a is joined by the outer quarter panel 12b. 
Meanwhile, the rear end cross member 10 is joined by side members 14, each member being lengthwise arranged along the body of the automobile at left and right side thereof.
However, there is a drawback in the rear portion of the body of the automobile comprising the quarter panel 12 joined by both tip end portions of the rear end cross member 10 and the rear end cross member 10 thus constructed according to the prior art in that the tip end portion of the inner lower quarter panel 12a of the rear end cross member 10 is directly joined by the inner lower quarter extension panel 12c of the quarter panel 12, such that, when an external force such as torsion or the like is applied to the joined portion between the rear end cross member 10 and the quarter panel 12, a crack or deformation can occur at the joined portion, thereby causing a structural problem of weakening a corner portion of the rear body.
Still worse, there is another drawback in that the weakened structural strength at the joined portion between the rear end cross member 10 and the quarter panel 12 causes the corner portion of the rear body to be twisted, thereby making it difficult to open and close the tailgate (T) when one wheel is placed on a non-planar location such as a hilly spot or the like.
The present invention is disclosed to solve the aforementioned problems and it is an object of the present invention to provide a rear end cross member reinforcement structure of automobile constructed to have respective members forming a rear end cross member join together to form a closed cross-sectional shape such that an external force applied from outside can be effectively diffused, and to have a structure at a joined portion between both tip end portions of the rear end cross member and a quarter panel changed to reinforce a structural strength relative to the rear end cross member, such that the rear end cross member can fully withstand an external force when the external force such as torsion or the like is applied thereto.
In accordance with the objects of the present invention, there is provided a rear end cross member reinforcement structure of automobile having a rear body including a rear end cross member arranged crosswise of the body and a quarter panel joining both tip end portions of the rear end cross member, wherein each tip end of an upper rear end cross member, a lower rear end cross member and an outer rear end cross member which form the rear end cross member is joined together to form a closed cross-sectional shape and both tip end portions of the rear end cross member is joined by the quarter panel to form another closed cross-sectional shape.